(1) Field of the Invention
The present invention relates to a discharge lamp provided with external electrodes, a production method of the discharge lamp, a backlight unit provided with the discharge lamp, and a liquid crystal display apparatus.
(2) Description of the Related Art
There has been known a discharge lamp provided with external electrodes, such as a discharge lamp 100 shown in FIG. 1 that is disclosed in Japanese Laid-Open Patent Application No. 2003-257377. The discharge lamp 100 includes a pair of external electrodes 101 and 102 which are fitted onto a glass bulb 103 at both ends thereof, respectively. In the discharge lamp 100 with such a construction, the corona discharge is easy to occur at the end portion 101a and the end portion 102a (not illustrated) of the external electrodes 101 and 102 on the glass bulb center side. The corona discharge becomes a cause of the generation of ozone. To prevent the corona discharge and the generation of ozone, the conventional technique covers the end portions 101a and 102a with insulating members 104 and 105, respectively.
However, with the construction of the discharge lamp 100, the lamp brightness is reduced at part 106 of the light extraction portion of the glass bulb 103 since the part 106 is covered with the insulating members 104 and 105. Also, the insulating members 104 and 105 become larger in the outer diameter in part where the insulating members 104 and 105 are provided. This prevents the discharge lamp 100 from becoming spindly and from having an excellent appearance.